The present invention relates to a pulley holder for supporting rotatably a pulley around which a belt is to be wound, and a drive transmission mechanism and an image recording apparatus using this pulley holder.
In an ink jet type image recording apparatus, the drive transmission mechanism that transmits a driving force to a carriage which is supported in a slidable manner in a predetermined direction has been conventionally known (see Japanese Patent Application Laid-Open No. 2005-313492). FIG. 1A illustrates a plan view of a known drive transmission mechanism 220. FIG. 1B illustrates a front view of FIG. 1A. The drive transmission mechanism 220 has such a structure that a driving pulley unit 233 and a driven pulley unit 223 are provided on a frame 221 such that the driving pulley unit 233 and the driven pulley unit 223 are positioned apart by a predetermined distance and an endless belt 222 is stretched between the units.
The driving pulley unit 233 includes a motor 236 arranged on a lower surface 221b of the frame 221, a motor shaft 235 that pierces through the frame 221 from the lower surface 221b to an upper surface 221a of the frame 221, and a driving pulley 234 coupled to the motor shaft 235. Further, the driven pulley unit 223 includes a pulley holder 225 secured to the frame 221 and a driven pulley 224. The belt 222 is stretched between the driving pulley 234 and the driven pulley 224. A rotatable force of the driving pulley 234 allows the belt 222 to circle around the pulleys. The belt 222 circling around the pulleys is coupled to the carriage and thus the carriage moves in association with the circular movement of the belt 222 in a predetermined direction.
FIGS. 2A and 2B illustrate enlarged detailed views of the driven pulley unit 223. FIG. 3 illustrates a cross sectional view of FIG. 2B taken along a line III-III. The pulley holder 225 generally includes a supporting arm 229 that supports the driven pulley 224 in a rotatable manner, an inserted part 238 that is inserted into an insertion hole 241 provided in the frame 221 (see FIG. 4), and a restricting part 226 that restricts a downward movement of the inserted part 238. In FIGS. 2A and 2B, a lower part of a lower surface 226a of the restricting part 226 in the drawing sheet is the inserted part 238. The inserted part 238 is provided with a stop part 227 projecting perpendicularly to the drawing sheet surface of FIGS. 2A and 2B. Further, a groove 228 is provided between the stop part 227 and the restricting part 226 to receive a corresponding fitting edge 242 (see FIG. 4) that is formed at an edge part of the insertion hole 241. Bottom surfaces 230 of the grooves 228 are angled with a predetermined draft angle φ.
In the pulley holder 225 having the above described structure, the inserted part 238 is inserted into the insertion hole 241 and the pulley holder 225 slides in a leftward direction in the drawing sheet of FIG. 4 (a direction as indicated by an outlined arrow), resulting in that the fitting edges 242 are fit into the grooves 228 while the fitting edges 242 contacts the grooves 228, respectively. As such, the pulley holder 225 is secured to the frame 221 in a vertical direction. Further, a fixture, which is not shown here, fixes the pulley holder 225 so as not to slide in a horizontal direction in FIGS. 2A and 2B.